Silica spherical particles for semiconductor sealing material

Abstract

The purpose of the present invention is to provide: silica particles of which the maximum particle diameter can be minimized and which can achieve proper fluidability that cannot be achieved by the conventional techniques; and silica spherical particles which, when used as a filler for a heat-dissipating sheet, can achieve excellent heat conductivity and flexibility. Silica spherical particles characterized in that, when particles each having a size of 5 μm or more and imaged by an optical measurement are observed, the particle diameter of each of the particles, which is determined from the image, satisfies the following requirements. Requirements: D99≤29 μm, and 10 μm≤Dmode<D99, and D99/Dmode≤1.5, and Dmode≤20 μm.

Description

TECHNICAL FIELD[0001]The present invention relates to silica spherical particles used for a semiconductor sealing material.BACKGROUND ART[0002]In recent years, semiconductor packages have become increasingly smaller and thinner. Particularly, in applications typified by smartphones, flip-chip connections that can be made thinner by multi-pins with a larger number of pins have been widely used, instead of conventional wire bonding. Flip-chip connection connects electrodes on a silicon chip and a substrate via minute solder balls, and has an advantage of saving space as compared with the conventional wire bonding portion. On the other hand, as the number of pins increases, a distance between adjacent solder balls becomes narrower, and a gap between the silicon chip and the substrate becomes narrower year by year (see Non-Patent Document 1). In the past, when such a narrow gap is sealed, sealing was performed with a resin alone without being filled with a filler. In such a case, it is ...

AI Technical Summary

Benefits of technology

[0028]The silica particles according to the present invention have a small maximum particle diameter and realize an appropriate fluidity that was not possible with the prior art. That is, it is extremely useful as a sealing material for semiconductors and the like that need to fill narrow gaps, exemplified in mold underfill.

[0029]Incidentally, two indicators of fluidity are used: a value obtained by a flow tester method, which uses a relatively high shear rate, and a value obtained by a rheometer method, which uses a slow shear rate. In the transfer mold, the flow velocity at the gate portion of the mold is relatively fast, and in the flow tester method, a smooth fluidity at the gate portion is suitably evaluated. From this point of view, in the flow tester method, a discharge rate is preferably 0.4 ml / sec or more, and more preferably 0.5 ml / sec or more.

[0030]On the other hand, a flow velocity of the sealing material in the semiconductor package portion is slower than that in the gate portion as a shear rate. In particular, the flow velocity of the underfill portion of the narrow gap becomes slow, and the flow velocity of the other overfill portion becomes relatively high. When such a velocity difference is remarkable, the easily flowing portion is preferentially sealed, and voids are likely to occur in the remained underfill portion. Therefore, it is necessary that the fluidity in the region where the shear rate is slow be kept within an appropriate range. From this point of view, the fluidity at such a slow shear rate is evaluated by the kinematic viscosity in the rheometer. The kinematic viscosity at 1 rad / sec was evaluated as a representative value. Here, the viscosity of 100 Pa·sec or more and less than 1500 Pa·sec is desirable, and further the viscosity of 400 Pa·sec or more and less than 1000 Pa·sec is desirable.

[0031]Further, in the heat dissipating sheet, the thermal conductivity is mainly influenced by the filler ratio as described above, and the sheet hardness is influenced by the fluidity of the filler. According to the present invention, it is possible to produce a heat dissipating sheet having excellent flexibility while increasing the filler ratio to obtain high thermal conductivity.

Problems solved by technology

In such a case, it is necessary to seal separately with a resin different from the resin for the overfill, which causes a problem that the productivity and the cost are greatly compromized.

In order to obtain a sufficient heat dissipation effect, the heat-dissipating sheet is required to be flexible enough to fill the gap generated by the surface roughness of the heating element and the heat dissipating component, since this gap will greatly impair the heat dissipation effect.

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